In vitro antimicrobial activity of the methanol extract and compounds from the wood of Ficus elastica Roxb. ex Hornem. aerial roots

Ficus elastica Roxb. ex Hornem., an edible plant belonging to the family of Moraceae, is traditionally used against skin infections and allergies besides having diuretic properties. This study aimed at investigating the antimicrobial activity of the wood of F. elastica aerial roots against a set of bacteria (Staphylococcus aureus; Escherichia coli, Proteus vulgaris, Providencia stuartii and Pseudomonas aeruginosa) and a yeast (Candida albicans). A mixture of linear aliphatic alkanes with n-hexacosane as major compound, β-sitosterol, biochanin A, sitosteryl 3-O-β-D-glucopyranoside (1), elasticamide (2), elastiquinone (3) and ficusoside B (4) were purified and characterized. Antimicrobial activities, expressed as minimum inhibitory concentration (MIC), indicated that the methanol extract showed MIC of 39.1 μg/mL; the lowest values were obtained for 3 and 4, with MIC as low as 4.9 μg/mL, smaller than the values of reference antibiotics (25 μg/mL). Furthermore, as most of the studied samples exhibited Minimum Microbicidal Concentration/Minimum Inhibitory Concentration (MMC/MIC) ratios lower than 4, a microbicidal effect was clearly exhibited. The overall results provided evidence that the wood of F. elastica aerial roots, as well as some of its isolated components might be potential sources of new antimicrobial drugs.